Pulse type telegraph receiver



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' PULSE TYPE TELEGRAPHHRECEIVR 'Filed June l?, 1943 I l I l lll.

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PULSE TYPE TELEGRAPH RECEIVER Filed June 17, 1943 v 5 Sheets-Sheet 2 jMfr-ammmm INVENTOR Y Hw ' ATTORNEY Jan. 4, 1949. w. H. Buss PULSE TYPE TELEGRAPH RECEIVER Filed June 17, 1943' 5 Sheets-Sheet `3? J w 1, MJ. WM n m p. w Z m A NS W n NSQMJ l A A A 4 W Y mm B m\\ n MMRMU Mmmm@ .ww V IIINNM IIIII ||%|\|.|\m.\h\ llllllll lll .u h QM P Qkuv, x@ 1-1.5-, U M rw n Q NQ uww\ k m I n mwhwd u \N\ rl u n uu, x .1.2 H l lll IIIIIIII lull.

Jan.-4, 1949. w. H. Buss PULSE TYPE TELEGRAPH `REKTEIVEYIR 5 Sheets-Sheet 5 Filed June 17, 1943 INVENTOR /mwf/v H. 54 Us.

ATTORN EY Patented Jan. 4, 17949 UNITED STATES PATENT oFFIl-CE `Warren .II-.' lulss'yOronm Mainaassignorto Radio CorporationiofAmex-ioa, a corporation oi- Dela- Ware Application. June 17, 194er` serialnm 4915088 Claims. 1

Radio telegraphlsystems employ either theiconventional Morse code or themulti-unit printer code. The Morse code employs unequal` length characters known as the dot and dash.Y Theftime duration of the dot is equal to thetime duration lof the baud which is the basictime unit, it being understood that the baud has a time duration of one-half a keying cycle at any speed. The time duration of the dash is equal to the time duration of three bauds or three basic time units.

transmitted for each dot and three such pulses are transmitted for each dash. The remaining portions of the dots and dashes are suppressed at the transmitter, and the signal is reconstructed at the receiver from the received short pulses.;

One such system is described in myV copending application, Serial #440.920, illed April 29, 1942, now U. S. Patent 2,365,450, granted `December 19, 1944.

The present invention speccally relates to the receiving system for reconstructing or rebuilding the received short pulses into conventional length telegraph characters.

One object of the present inventionis to provide an alternative and improved system for re'- constructing received short pulses carrying telegraphic intelligence into conventional code characters.

Another object is to provide areceiving system for reconstructing short pulses of received energy into conventional code characters but whichlis ineffective or blocked during the intervals between the received pulses, so that spurious sig.- nals (such as from noise and interference) will not affect the operation of the receiver;

Since the receiving system of the presentinvention operates on the principle of pulses,.the

ringbetween signall pulses :from affectingthe system and for tripping the tubes. ofV therregeneratreceiver is adjusted to operate at the sameiun'- damental pulse frequency as the transmitter, and synchronized as to phase by the incomingpulses.

In accordance with one receiver embodiment of the invention, apparatus is providedfor converting the received pulses into signals representing dots and dashes. The incomingpulses are applied to a twotube gas triode reshaper: This reshaper operateslon the arrival of eachfpulse or..` In` a modification off thisembodimen't, the local-:oscillator is also usedfor terminating the reshapedpulses@` Iii-.anotherfembodiment of` the invention, only y,v-accumttube circuitsl are employed to achieve the results` of theinVentiOn, thus providing a more stable and simplified-arrangement.than that Vutilizing gaseous tubes.

Qther. objectsfof the invention will# appear' from alreadinglofl the followingdescription, `which is accompanied by ai drawing,` wherein:

Fig,- 1: illustrates oner embodimenty of a `receiv ingtsystem constructed iniaccordance W-ithr the principles"` oi the i present` invention; i Fig.; 2.1illustrat'esdetailthe phase shifting circuit fernployedfirrFig. 1;

lS'ig-r` 3" illustrates afseriesof curves representingwoltage variations at Various designated points inrthe: circuit of thereceiver of Figflr;

xFigs. 4- and.:5 `illustrate preferredtformsrof re'- ceivling 1 systems of' the invention; and

Fign illustrates arseries of curves representing voltage variations at designatedA points: in the circuits of the receiversof Figs:` 4` and 5;

. The i complete: radio` telegraphI receiving system ofFig. 1w, includes` essentially the following. ap,- paratusir" A diversityfreceiver for co'llectingetthe incoming signals; a'lpulse: reshaperA fed: icy-the diversityreceiver, 'a vacuuml tube 1lockingcircuit` fed by=therreshaper andfla I"local synchronized oscillator. The vacuum tube locking circuit is cone trolled-hoth by thespulsewreshaperl and by theout` putl` of' theloscillator. throught:suitablefphase shift-` ing apparatus;` T'lie local oscillator is'` controlled as tovphase4 by pulses fromlthel'pulserreshaper through.' al. suitable .10W i pass filter; The output circnitffor the system; which maybe anysuitable' titilizatiorrV circuiti',4 such `as.` ai recorder' or printer,`

ltiometer I9.

antennas and 2 and amplied, detected and i' combined in the apparatus 3, 4 and 5 in well known manner. and the rectified signal pulses applied to the grid of tube Bof the reshaper circuit through a current limiting resistor 8.

shifter 22 and through this phase shifter to bias' potentiometer 32. In effect, the locking circuit composed of the two tubes 2l and 3| has two degrees of electrical stability. These tubes are unstable when both are drawingv current, but stable when one tube is passing current and the other tube locked Aor. prevented fromY passing current.

The'f'change'from one condition of stable equilibrium, such as when tube 21 is blocked and tube 3| is passing, to the other condition when tube 21 is passing and tube 3i blocked, or the reverse, is caused by the presence of a suitable predetermined potential applied to a grid of the locking F'cir'cuit. IThis 'form of locking circuit is well The term reshaper has here been employedv because the circuit converts the shape of an inv itiating pulse applied to the grid of tube Ii into a vsubstantially square or rectangular pulse irrespective of the shape of the received initiating pulse. More specically, the "reshaper cornprises a pair 4'of grid-controlled gaseous triode tubes 6 and 1 interconnected in the manner of a balanced or stable trigger circuit having two degrees of electrical stability and which requires an initiating pulse to change the condition of equilibrium. Gas tubes 5 and 1 are known in the art as Thyratrons These gas tubes have plate resistors 9 and II) connecting the plates to a source of positive plate polarizing potential, and have cathode resistors i2 and I5. These cathode resistors are by-passed by condensers I3 and I6 which serve the improve the rectangular pulse wave form obtained from the reshaper. A commutating condenser Il connects the plate of tube 5 to the plate of tube 1. Normally, gas tube 6 is non-conductive while gas tube 1 is conductive. The application of a signal or initiating pulse of positive polarity to the 'grid of tube yIi will cause this tube to conduct, asv a result of which tube 1 will cease conducting by virtue of 'the commutating action of condenser I I. Putting it inA other words, an initiating pulse will nre or trigger off the reshaper fromvone stable state in which tube 1 is normally conducting and tube 6 normally non-conductive to the other stable state in which the current passing conditions of these two tubes are reversed. Output energy from the reshaper in the form of square or rectangular wave pulses is taken from the cathode of tube 6 by way of lead 95` and applied both to the vacuum tube locking circuit through resistor 29 and to the low pass filter. The cathode of tube 'I is connected to the vacuum tube locking circuit through a resistor I1. The grid of tube 1 is connected through current limiting resistor I4 and phase shifter 2| tothe sliding contact of poten- Potentiometers I8 and I9 provide means for supplying and adjusting the grid bias on the triodes 6 and 1, respectively.

The vacuum tube locking circuit, which can be referred to as a balanced trigger'circuit, comprises a pair of vacuum tubes 21 and 3| whose grids and anodes are interconnected by means of resistors 25 and 26. Tube 21.is later referred to as the space tube, while tube 3| is later referred to as the mark tube. Plate resistors 23 and 24 connect the plates of tubes 21 and 3| respectively to the positive terminal of a source of plate polarizing potential B+. The cathodes of tubes 21 and 3| are connected together and directly lto ground through a common ground potential bus 81. The grids of tubes 21 and 3| are connected through resistors 28 and 30, respectively, to phase known'inthe art, and a more detailed description of the general operation thereof may be had by referring to United States Patent #1,844,950, granted February 16, 1932, to James L, Finch. One characteristic of this locking circuit is that it remains in a particular condition of stability until such time-as a pulse of suitable polarity impressed thereon serves to change the condition of electrical stability.

The local oscillator comprises a pair of amplifier tubes 'lll 'and 55 arranged in a regenerative circuit. The grid'of ltube 55 obtains energy from the plate oi' tube lil' through blocking condenser 39 and in turn supplies feed-back energy from its plateto the grid of tube 4l' through condenser `52*andresistorll. The oscillatory circuit comprisesan inductance coil 45 and a condenser 5 connected between the grid of tube l and the cathodevasshown. The plates of tubes l1 and 55 are supplied with positive polarizing potential through resistorst and 58, respectively, connected to the common plate supply lead extending to terminal B+. AThe oscillator is designed to produce oscillations of sinevvave character and 'of an audio frequency which is the same as the fundamental pulse frequency ci the transmitter. 'An oscillator of this general type is described in VVgreater detail in United States Patent #2,162,520, granted toJ. N. Whitaker,-June 13, 1939, to which reference is made. The local oscillator is syn.- 'chronized by means "of pulses derived from the Cathode of gas tube ii of the reshaper and appliedto lead`95. These synchronizing pulses, which are of rectangular shape, are fed to a low pass filter' consisting of coil 135 and shunt-con Vnected condensers G3 and 54 from which the filtered energy is supplied to an auxiliary ampliner tube 59 whose plate circuit is coupled to the grid ofmtube 55 of the local oscillator through a condenser 51. The low pass lilter is terminated by resistors E2 and liti of suitablevalues from an impedance matching standpoint. The cut-olf frequency of the filter is arranged to be at a value slightly above the fundamental pulse fre quency at which the local oscillator operates. Auxiliary amplilier tube 5S is provided with a i plate resistor 53 connectedto the positive terminal B+ of the source of plate polarizing potential and is also provided with a cathode resistor Si shunted bya by-pass condenser 59. The lou1 filter serves to remove most of the harmonic content vof the essentially square pulses, and.V to change the shape of these square pulses to a resulting wave which is approximately sine wave in shapaand it is this last Wave which is applied to: tube 59. 'y

:.'Ihe'output of the local oscillator. is applied to. the grid of amplilier tube 42 having the usual cathode--resistorlt and shunt condenser 44. The plate circuit oftube 42 includes an audio irequency transformer 4| Whose secondary winding is coupled to the three phase shifters 20, 2`I and 22,

The circuit of the phase shifters 20, 2| and 22 is shown in more detail in Fig. 2,.which illustrates by way oi eXample one form which these phase Shifters may take. The phase shifter of Fig. 2 comprises an input transformer 68 Whose primary winding is coupled to input terminals` 61, an output transformer 'I4 whose secondaryr Winding is coupled to output terminals 15, and a vacuum tube 'II coupled between the secondary winding of transformer 68 and the primary winding of transformer 'dit l The secondary winding of transformer til has one terminal connectedto a Variable resistor lil. Condenser 69 and resistor "ID are directly connected to a common lead extending to the grid of tube 'II, as shown. TheV midpoint or center tap of the secondary winding of' input transformer' t8 is connected to the negative terminal of a battery or source of `unidirectional poten.- tial 13, whose positive terminal is connected to the plate oi tube il through the primary winding of output transformer 'ik The cathode of tube il is also connected to the center tap of the secondary winding of input` transformer 6B through a biasing resistor 12. output from the plate circuit of' tube 'Ii appears at terminals '15.

These phase Shifters are of the` constant capacitance-variable series resistance type whose operation is familiar to those skilled in the art. By means of suitable values of capacitance and resistance for a given frequency, the output phase can be adjusted over a range or nearly 180 as the resistance is changed from its maximum Value to zero. The magnitude of output of each phase shifter is determined by the turns ratio of the output transformer.

The regenerated or reconstructed code characters from the system of Fig. 1 are derived from terminals 3l, one of which is connected to the cathode of the output coupling tube 34 whose grid is connected through resistor 33 to the plate ci tube 27 of the locking circuit. Bias for the grid of coupling tube 34 islobtained from a tap on potentiometer 39 through an input resistor 35. The plate of vacuum tubel34 is connected directly to the positive terminal B-I- of the source oi plate polarizing potential.

It should be noted at this time that the lower` terminals of potentiometers I8, I9, 32 and 39 are directly connected to the negative terminal of the stable source of unidirectional potential, While the upper terminals of these potentiometers are directly connected to ground by means of bus or common lead 81. l

An understanding of the operation of the system of Fig. 1 may 'be had by referring to Fig. 3, which shows a series of curves 'I6 to 86, inclusive, representing voltage variations at various designated points in the system of Fig. 1. Let it be assumed that Morse code characters are being transmitted and that the dot frequency is 50 dot cycles per second. With this assumption, the fundamental pulse frequency is one hundred pulses per second, in which. case the local oscillator lll, 55 will 4be arranged to produce sine wave oscillations of a frequency of one hundred cycles per second. The low pass lter 63, 64 and 65 will therefore lbe set at a value slightly above the fundamental pulse frequency of one hundred pulses per second, and should have a cut-off frequency of, let us say, 150 cycles per second. Let l it also be assumed that theletter. R,` in Morse code characters is being received. This VIletter R come The phase shifted prisesfa dot; adashranda dot. Atthe transmitted: only a `short pulse will be transmitted ion eaclr` basic unit of the signal, so that` the letter Riwllt be transmitted in the formtof?` a ksh'ortpulse forx the` dot, threefshort spacedlpulses'for the dasl-n. and another` short'pulse for thefsecond dot.' otfthis. letter. Curve or Wave form 'lxshowsl atypicall incoming signal for the letter R: as observed* atthe: output terminals of the combining unit 5. oi..Fl`g.1 l for a pulseltypetelegraph system. Thethree: pulses `in the center. constitute. thel dash` of: the: letter R; l A noise `peak589 is shownuasl appearing: betweenthe last twoiy received pulses',` that. 1albetween thedash and theA last dot. These incoming?, received` pulses represented by curvey I6l arelape plied directly to the grid of thesgas-.trio'deffof the reshaper, in combination.` withl a` blocking. sine wave represented |by curve `IlIl-iemanating from; phase shifter 20S. The combined. wave or total electromotive force of both4 the incoming' received signal andthe output of the phase` shifter: ilIlisA represented by the wave formvof curvel. Thislwave formhas beenv labeledEgs, because itl is thevolt'age Wave applied? to the grid of; tubeA 6r off the reshapen Horizontal line SIlfof Wave form: 8I represents the critical cut-off potential for gasr tube 6 below which the tube remains in its nor-- mal state.` of. non-conductivityJ andi above which: the tube 6 lires or triggers off to reverseithestates'l of4 conduction of theztwolgas tubes` 6 andi 'It It` will be seen from the curve 8'I that thevolta'gef wave applied to the grid of tubetlfrisesabovethef cut-off valueat times. corresponding tev the times of the received signal pulses; Thus, theI tube 6 will fire with thearrival of each received pulse to produce a rectangular or. square waveV output pulse represented by curve 11. The output of tube 6 (as indicated by curve TI) is derived from the cathode of tube 6 by Way of leadi95.

It` should be noted that wave form 'I6 includes a spurious signal at 89; representative of anoise'V or interference peak. This noise peak 88, how--` ever; will not cause a false firing of tube 6 because the combination thereof with the blocking elece tromotive force sine; wave represented by curve" 80V willl produce a resultant whose position'rlfalls' below'the critical value, as shownin the combined Wave form 8| at point 89. By proper adjustment of` the phase and magnitude ofvthisl blocking wave constituting the output ofthe phasey shifter 2li,` the eifect of most ofthe received noise pulsesf'is* eliminated.

The ring or triggering off the reshaper"` by meansiof the` pulsesf applied to the'grid 6, reverses the states of conduction ofthe two gas tubes Wand-f 'L The reshaper circuit willfl'be" restored tolitsft original condition ofI equilibrium atl a` time-in'- terval shortly after the` applicationofanr initiating pulse to` the tube 6 when af pulse of positive polarity is*` applied` to the e'lid of tube 'I bythe phase shifter 2|'. Curve 82 represents thewave form constitutingthe output of the phase shifter 2Iwhich` is applied through resistor I4'l tothe grid of' gas tube I, The output' of phasesliifterf 25| res the tube l andcau'ses itlto regain its' norl mal condition of conduction soon after the arrival ofv such signal pulse. The output of gas tube YIl is` taken from the cathode of this tube and is rep-` resented by curve 'IBL Thesquare or'rectangular` wave'` obtained from gas tubes 6 and 'I` and representedlbyfcurves 'I1 and 18; are ofopposite polare ity.:

The outputoi the reshaper,as obtainedfrom' lead and represented byv curve 1T, is used'fto l produce the regenerated or reconstructed signals sarge-v4 and. to'also' control the synchronization of the local oscillator 41, 55. For this last purpose, the square wave p-ulse's of curve 11 are applied to the grid ofuamplii-ler.` tube 59 via the single section low pass filter which, for the assumption of aA fundamental pulse frequency of 100, should have atout-oir frequency of about 150 cycles per second.. The resultingpulses from the output of the single section low pass lter which are approXimately sine wave in shape, are amplified by tube 59'and then applied to the grid of the oscillator feedback tube 55 along with the normal amplied oscillations supplied from tube 41 of the oscillator.V If the phase of the local oscillator thus tends to advance or retard, relative to the fundamental pulse frequency cycle, the incoming pulses automatically correct it.

y, ICurves-lill, S2 and 83 illustrate the wave forms of the outputs of phase shifters 20, 2| and 22, respectively, and their relative phases, while curve 1Q represents the wave form output of the local oscillator. vThe relative phases of the outputs of these phase Shifters are adjusted so that their associated circuit perform their intended functions properly. The locking circuit composed of interconnected tubes 21 and 3| serves to regenerate or reconstruct the incomingy received pulsesint-o` full length code characters such as d ots` and dashes. The grid of mark tube 3| has applied to it the output of tube 6 through resistor 29 and represented by curve 11, combined with the output of phaseshifter 22 through res istor 3|] and represented by wave form 83. This combined wave form applied to the grid of tube 3| is represented by curve 85, 'and will cause Vthe tube 3l to lock into a state of conduction whenever its ,grid potential rises above the critical value shown by the dotted horizontal line 8| of curve 85., This dotted line 9| represents the cutoff value of this tube. The tube `3| will start to conduct if it already is notJ in a state of conducn tion, and ir" it is ina state of conduction it will remain locked in this condition by the application of a potential to the grid of, this tube above the critical value, vuntil such time as the space tube 21 is caused to pass current. Tube 21 has applied toits grid the output of gas tube 1 through resistor l1 which has a wave form represented by curve 1,8, combined with the output of phase shifter22 through resistor 28 and which has a wave form i. represented by the curve 83. This combined wave form of the voltage applied to the grid of the "space vtube 21 is represented by the curve. Tube 21 willtake over control from the tubel3| and will pass current each time the gridvoltage Egrz` rises above the critical value shown by the dotted'horizontal line 92 of curve 85. By comparing the wave formsof curves 84 and 85, representing the voltages applied to the grids of tubes 21 and 3i respectively, and noting when they rise'above their respective critical values, (shownby horizontal lines 9| and 92, respectively) it will be seen that tubes 3| and 21 of the locking circuit will produce a mark and space wave formas illustrated by curve 86. This curve 86 represents the fully regenerated or reconstructed waveform for the letter R and is actually produced as the variation in voltage at the plate of tube 21. The voltage of wave form 86 is applied to the grid of the output tube 34 through resistor 33 and the regenerated signal is taken from the cathode circuit of the coupling tube 34 by means of terminals 31 forsubsequent utilization by a recorder or othervsuitable circuit. Y Eig. 4 illustrates an embodiment of the inven- 8 tion which isV more simplified than the lsystem of Fig. 1, in employing, among other things, a more reliable arrangement for tripping the two-tube vacuum triode locking circuit. The system of Fig. 4 has the advantage over Fig. 1 of employing only two phase Shifters. Referring to Fig. 4 in more detail, there is shown a receiving system |00 which represents any standard continuous wave radio receiving system whose output, taken with positive polarity, is applied to the reshaper comprising gas triodes |04 and ll. This re- Shaper is an unbalanced trigger circuit. The gas triodes |04 and l lil are supplied with cathode resistors |01 and ||2 and with plate resistors |03 and |55, respectively. The cathode resistors |01 and I2 are b 7-passed by condensers |08 and ||3, respectively. A commutating condenser |06 is connected between the plates of the two gas tubes. The outputs of the gas tubes |834 and H0, taken from their cathode circuits, are applied directly to the plates of vacuum triodes ||6 and H1, whose grids are directly connected together. A portion of the output of gas tube Il is also supplied to the synchronized oscillator |30, the

. lter and auxiliary tube being here omitted. The

reshaper is a form of unbalanced or unstable trigger circuit in which tube S4 is normally nonconductive and tube ||0 normally conductive. Tube Il@ will hold its state of conduction except when an incoming pulse iires tube |64, in which case the current passing conditions of the two tubes will be reversed. After a time predetermined by the bias setting for tube I0, and the constants of the circuit, this tube will recover conduction and tube |434 Will again become non-conductive.

The reshaper serves to provide rectangular or square wave output pulses irrespective of the form of the incoming short pulses.

The oscillator I3|l is substantially the same as that illustrated in Fig. 1 and provides an output which is fed into two conventional variable phase Shifters |3| and |32 of the type previously described in connection with Fig. 2. The output of phase shifter |3| is supplied in series with the incoming signal to the grid Hill through resistor |52, and the output of phase shifter |32 is directed into a wave form distorting circuit consisting of vacuum triodes |33l and linterconnected as shown. A xed bias is produced on tube |33 by means of resistors |3l| and |35, and this tube is coupled by condenser |31 to the grid of tube |45 which operates as a class A amplifier. The output of tube Mil passes through a transformer I4! whose secondary winding is shunted by a potentiometer M2. YA tap on potentiometer |42 feeds energy over lead directly to the grids of both tubes ||6 and ||1 The cathodes of tubes ||6 and ||1 are connected to circuit elements of a vacuum tubelocking circuit comprising tubes |2| and |26. The anodes and grids of these two tubes of the locking circuit are interconnected by means of resistors ||9 and |20. Grid resistors |22 and |24 are shown connected to the grids of tubes |2| and |25, respectively. A common cathode resistor |23 is provided for both tubes of the locking circuit. This locking circuit is also provided with plate resistors I8 and |25, both of which connect to the positive terminal B-lof a source of unidirectional plate polarizing potential. The locking circuit has two degrees of electrical stability, and functions generally in the manner of the locking circuit of Fig. 1. It should be noted that resistor |22 is common to the cathode of tube |`|1 and thegrid of tube |2|, and that resistor |24 is common to the cathode of tube II6 and the grid of tube |26. The output of the locking circuit, taken from the plate of triode I2 I, is applied to a suitable utilization device, which may be a recorder, by means of a driver tube 29 whose grid is connected to the plate of tube |2I through a battery |21 which maintains proper bias on the grid of tube 2B.

The operation of Fig. 4 will now be given with particular reference to the series of curves |12- |16, inclusive, of Fig. 6. Incoming pulses, as illustrated b-y the wave form of curve |12 of Fig. 6, are applied to the control grid of gas tube |04, Which produces a conduction versus time relationship as shown by the wave form of curve |13. The conduction versus time pattern of tube I I is given by the Wave form of curve |14 and is the inverse of the wave form of the curve |13. These curves |13 and |14 are developed as voltages across the cathode resi-stors |01 and II2, respectively, and they are also applied as the anode voltages to vacuum tube triodes I|6 and |I1, respectively. The oscillator is maintained in synchronism with the incoming signals in the same manner as described in connection with Fig. l, and the output of phase shifter I3I is used for noise blocking purposes, also in the same manner as explained above in connection with Fig. l. The output of phase shifter |32 is clipped or limited by the vacuum tube |33, which is over-biased, and this output is further distorted by the intentionally poor response of transformer |4I. The resultant wave form obtained from potentiometer |42 and applied to the grids of tubes I|6 and I I1 by way of lead |59, is shown in the wave form of curve |15. It should be noted that this wave form is very peaked for the purpose of reliably and quickly tripping the locking circuit.

The wave form |15, it -should be noted, comprises a multiplicity of trigger pulses labeled a to z', inclusive, and these trigger pulses are applied simultaneously to the control grids of tubes I'I6 and I l1 at the proper phase by virtue of the phase shifter unit |32. The outputs of tubes I|6 and ||1 consist of similarly sharp pulses developed across the cathode resistors |24 and |22 of the locking circuit. However, these output pulses, which become the input or tripping pulses for the locking circuit, do not occur simultaneously across both `of the resistors |24 and |22 because of the distributed manner in which plate potential is supplied to triodes I I6 and I I1 by the reshapen Since the tube .|16 receives plate potential only during the intervals indicated by the wave form or curve |13, it is evident that only pulses b, d, f, g, h of wave form I 15 will be transferred on to the control grid of triode |26. Likewise, since tube M1 is supplied with plate potential, as indicated by the wave form of curve |14, only pulses a, c, e and z' of wave form |15 will be applied to the grid of triode I2I of the locking circuit.

The functioning of triodes I`2| and |26 is such that at any given instance one tube only conducts plate current while the other is driven to or beyond cutoff. A positive pulse applied to the grid of the non-conducting tube will flip or swing this tube into conduction and the other will be driven to cut-off. A positive pulse applied to the conducting tube will have no effect. A comparison of the wave forms ofcurves |13, A|14 `and |15 will show that tube |26 will have a conduction versus `time characteristic as `illustrated by the wave oicurve |16, iwhile tube I2| will have an inverse characteristic.

'Wave form |16 is developed as the voltage variation at the plate of tube I2I and is used to drive the recorder or other utilization apparatus by means of ampliiier tube 29 and represents the regenerated or reconstructed code signal of the remote transmitter.

Fig. 5 is a modication of the system of Fig. 4. The boxes of both of these gures which are similarly labeled contain apparatus which function similarly to those of Fig. 4, except for certain slight differences which will be pointed out later.

Referring to Fig. 5 in more detail, the output of the receiving system |00 is supplied through a half wave rectier |45 to a condenser |46, and also supplied directly to the oscillator |30 for synchronizing purposes. The two phase Shifters i3! and 32 are the same as those of Fig. 4, except that the output of phase shifter I3I is fed in series through the secondary winding of transformer |44 to provide the desired noise blocking effect between impulses in the charging circuit of the condenser |46. The output of phase shifter |32` is fed to the wave form distorting circuit composed of vacuum tube triodes |33 and |40. This part of the circuit is also similar to that of Fig. 4, except that its output from transformer I4I is fed through `potentiometer |42 to the grid of vacuum triode |41, and also Vthrough a resistor I 24 to the grid of tube|26. The discharge circuit for condenser |46 is `through triode I 41 and resistor |22. Resistor `|22 is also the grid input resistor for triode |2| Which operates in conjunction with triode |26 as a locking circuit. The remainder of the locking circuit with the driver tube |29 is substantially the same as that of Fig. 4.

A description of the operation of the system of Fig. 5 follows: The incoming pulses represented by the wave form of curve |12 of Fig.. 6 are allowed to charge condenser |46`through rectifier |45, provided at the time of the incoming pulses the sine wave output of phase shifter I3I is at its positive peak value, In other words, the positive peak of the output of phase shifter |3| adds with the incoming pulse to provide a resultant `wave whose peak exceeds the value :necessary to operate rectifier |45. Shortly after the rrival time of each of these incoming pulses, the condenser is discharged through triode |41 through the application of a peaked pulse from the transformer I4I. These peaked or trigger pulses are shown as the wave form of curve |15 of Fig. 6. Since the disharging of condenser |46 takes place through resistor |22, a tripping pulse will be passed on to tube IZI of the locking circuit for each incoming pulse. Conduction will be switched each-such time from tube |26 to tube Iii, if the former is not already in a state of conduction, in which case, if it is in a state of conduction, it will remain so. The bias for triode |41, while tube |28 is conducting, is obtained as the IR drop across resistor I 22 and is sufficient to prevent the discharge of condenser |46 prematurely, The trigger pulses ofcurve |15 are also applied to the grid of tube |26 at lesser magnitude than those applied to tube |2| because of the series resistor |24. Hence, at the periods when no discharge of condenser |46 takes place (no incoming pulses having been received), tube |26 will be tripped by the trigger pulses and it will take conduction from tube I2I. Reference to Wave form |12 and |15 of Fig. 6 reveals that condenser I 46 will Yreceive charges just preceding trigger pulses b, d, f, g, and h and will be dis-` 11 charged by these trigger pulses so as to trip tube 52| of the locking circuit or keep it tripped as in the case of pulses g and h. These same pulses b. d, f, g and h are also applied to the tube |25 ti'nough resistorldi but have no effect here since the simultaneously applied pulses at tube IZI predominate. lLIowever, the trigger pulses a, c, e and i will be effective in tripping tube |26, The results of the above switching combinations will give conduction versus time characteristic for tube iti as shown by Wave form 116 of Fig. 6. Thus, the regenerated signal and its voltage variation selected from the plate of tube E25 to operate the recorder or other utilization device through the driver tube E29. Since most noise peaks are shorter in duration than the regular incoming pulses, it is preferred (in the operation of the system oi Fig. to so adjust condenser Ill-' in as to absorb such peaks Without develOp. g high. enough voltage to cause false tripping oi the locking circuit.

What is claimed is:

l. In a pulse communication system, a receiver having means for collecting the incoming pulse signals, an electron tube trigger circuit, an audio frequency oscillator operating at the fundamental pulse frequency, means for combining the output of said local oscillator with the output of said receiver and applying the resultant Wave to said trigger circuit, said means including a phasing circuit, and means for synchronizing said oscillator from said trigger circuit.

2. In a pulse receiving system, an electron tube trigger circuit, a generator of oscillations operating at the fundamental pulse frequency, means for applying the incoming pulses and the output of said generator to said trigger circuit, said means including a phasing circuit for assuring that the positive peaks of output from said generator combine with the incoming pulses to produce a resultant Wave Yform Whose positive peaks exceed the critical value required to change the condition of electrical stability of said trigger circuit, a locking circuit in the form of a pair of vacuum tubes so interconnected as to have tivo degrees of electrical stability, and individual connections from the electron tube trigger circuit to said vacuum tubes for controlling said locking circuit in dependence upon the condition of electrical stability of said trigger circuit.

3. In a radio telegraph signal receiving system for receiving pulses representative of intelligence signals transmitted from a remotely located radio transmitter, an unbalanced trigger circuit having only one degree of electrical stability, said trigger circuit comprising rst and second gase ous grid-controlled tubes so interconnected that only one of said tubes is conductive at any one time, said irst tube being normally conductive and said second tube being conductive for only a short period after an initiating pulse is applied tosaid trigger circuit, a lsine Wave oscillator operating at the fundamental pulse frequency, and means for combining the sine wave output of said oscillator and unidirectional pulses representative of the received pulses to control said trigger circuit, said means including a phasing circuit for assuring that the peaks of predetermined polarity o the sine Waves combine in phase with the polarity of the unidirectional pulses.

4. In a radio receiving system for receiving pulses of energy representative of intelligence signals transmitted from a remotely located radio transmitter, an electron tube trigger circuit Aof the double stability type always requiring the application thereto of a Wave of predetermined polarity to change the condition of stability for converting the incoming pulses to rectangular wave pulses, a generator of sine Wave oscillations operating at the fundamental pulse frequency, and means for combining said sine wave oscillations and the incoming pulses and ior applying the resultant wave to said trigger circuit, said means including a phasing circuit having a range of substantially ior assuring that only the peaks of positive polarity of said sine Wave oscillatons are combined in phase with the incoming pulses to produce resultant peaks having a value exceeding the critical value required to re said trigger circuit. l

5. In a pulse receiving system, an electron discharge device trigger circuit for converting the incoming pulses to rectangular Wave pulses, said trigger comprising a pair or grid-controlled gaseous tubes so interconnected that only one of said tubes isconductive at any one time, a generator of sine Wave oscillations operating at the fundamental pulse frequency, means for combining said sine Wave oscillations and the incoming pulses and for applying the resultant wave to the grid of that tube which is normally non-conductive to thereby alter the condition or electrical equilibrium of said trigger circuit, and a circuit forv applying the sine Wave oscillations of said generator to the grid of the normally conductive tube to restore the normal condition of equilibrium of said trigger circuit, said last circuit including a phase shifter.

6. In a pulse receiving system, a trigger circuit for converting the incoming pulses to rectangular Wave pulses, said trigger circuit comprising a pair of grid-controlled gaseous tubes so interconnected that only one of said tubes is conduc tive at any one time, a generator of sine Wave oscillations operating at the fundamental pulse frequency, means for combining said sine wave oscillations and the incoming pulses and for applying the resultant Wave to the grid of that tube which is normally non-conductive to thereby alter the condition of electrical equilibrium of said trigger circuit, saidk means including a phase shifter for assuring that the positive peaks of said sine Wave oscillations combine in phase with the incoming pulses to produce resultant Waves With peaks having values exceeding the critical value required to change the normal condition of equilibrium of said trigger circuit, and a circuit for applying the sine Wave oscillations of said generator to the grid of the normally conductive tube to restore the normal condition of equilibrium of said trigger circuit, said last circuit including a phase shifter.

7. A system as dened in claim "l, including another trigger circuit having two degrees of electrical stability, said last trigger circuit including a pair of vacuum tubes having their grids and anodes interconnected so that only one Vacuum tube is conductive at any one time, separate connections from the grids of said vacuum tubes to the outputs of said gaseous tubes of said first `trigger circuit, and means for supplying the grids pair of grid-controlled gaseous tubes so interconnected and biased as to have only one degree of electrical stability, `oneof said gaseous tubes being normally conductive and the other tube normally non-conductive, a generator of oscillations of a frequency equal to the fundamental pulse frequency, means including a phase shifter for combining said oscillations with the incoming pulses and for applying the resultant Wave to the grid of the normally non-conductive tube to thereby alter the conditionxof electrical stability of said trigger circuit, the constants of said'trigger `circuit being such` that said trigger `circuit restores itself to normal aftera predetermined time interval, a pair of vacuum tubes each having .plate7 grid and cathode electrodes, connections from the plates of saidvacuum tubes to dierent outputs -of .said gaseous tubes. whereby said plates obtain at different `times from said trigger circuit the polarizing potentials :necessary to `enable the vacuum tubes to conducteurrent, and means including a phase shifter coupling the grids of said vacuum tubes in common to saidgenerator. v i

9. In a pulse receiving system, an `unbalanced trigger circuit for converting theincoming ,pulses to rectangular wave pulses, said trigger circuit comprising a pair of grid-controlled gaseous tubes so interconnected and biasedcas to have only one degree of velectrical stability, one `of ysaid gaseous tubes being normally conductive and the other `tube normally non-conductive, Aa synchronized generator of sine wave oscillations of alfrequencyequal tothe fundamental pulse frequency, means including a phase .shifter .for combining said oscillations with the incoming pulsesfinsuch phase Ithat the positive peaks `of the `sine wave oscillations add 4with incoming pulses tot produce a resultant wave form whose peaks exceed kthe critical value required. to nre said trigger circuit, and for applying the resultant Wave to the grid of the normally non-conductive tube ,to thereby alter the condition of electrical stabilityof said trigger circuit, the constants of said trigger circuit being such that -said `trigger restores itself to normal after a predetermined time interval, a pair of vacuum `tubes each having plate, grid and cathode electrodes, connections lfrom the plates of saidvacuum tubes Ato different outputs of said gaseous tubes, wherebysaid plates obtain at different times from said trigger circuit the polarizing potentials necessaryito enable the vacuum tubes to conduct, andrmeansincluding a phase shifter coupling thegrids oisaid vacuum tubes in common to said generator. i

10. `In a pulse receiving system, :a generator of oscillations operating at `the `fundamental pulse frequency, a storage element, mawrectiiier coupled to said storageelement,means for applying `the incoming pulses `to `said rectifier including a transformer, `means `including said-transformer and a phase shifter for applying said os-` cillations to said rectifier, a space discharge cir"- cuit for said storage element2 and meansfincluding a wave distorter coupling the output of said generator to said space discharge .circuitfor ,applying periodically recurring peaked waves tosaid discharge circuit at the frequency `of said generator, and an electron tube `trigger circuit coupled to said space discharge circuitwand responsive to theilow `of currenttherethrougln ll. ln a pulse receiyirrg system,',a `synchronized generator of oscillations ofsinewave form operating at the fundamental pulse frequency, a storage condenser,` fa rectier coupled to said storage condenser, means for applying both the incoming pulses and output energy from `said generator to said rectifier, said means including a phase shifter for `assuring that the positive peaks ofsaid oscillations additively combine with incoming pulses to increase the resultant rectified stored energy on said condenser, a discharge path for said condenser comprising a vacuum tube having a control electrode, and a circuit'for rendering said vacuum tube conductive shortly after the arrival of each incoming pulse, said circuit including a phase shifter coupled to the output of said generator, a wave distorter whose input is coupled to said phase shifter and whose output is coupled to the control `element of said vacuum tube, said Wave distorter altering the sine waveform of the oscillations impressed thereon to a wave form having accentuated peaks recurring at the frequency of said generator.

12. In a pulse type communication. system wherein pulses are transmitted whose time duration is shorter than that of the pulse corresponding to one-half a keying cycle, `a receiving system including signal regenerator receiver for rebuilding the received pulses into` longertime duration units, said receiver comprising alocal oscillator producing sine Wave oscillations synchronized by the incoming pulses and operating at the fundamental pulse frequency, a balanced electronic trigger locking circuit under control of both the incoming pulses and the output of said oscillator, said trigger circuit comprising a pair of vacuum tubes so interconnected and biased that when one tube passes current the other tube is blocked, and vice versa, saidtrigger circuit having two degrees of electrical stability and always requiring the application theretoof a waveform of predetermined polarity to change the condition of stability, and a vacuum` tube phase shifter having a range-of` approximately 180 located between the sine wave output of said oscillator and the input to said trigger circuit,

as a result of which oscillations of sine` wave form are applied to said trigger circuit,

13. In a pulse receiving system, an unbalanced trigger circuit for converting the incoming pulses to rectangular wave pulses, said trigger circuit comprising a pair of grid-controlled gaseoustubes so interconnected and biased as to have only.

in such phase that the positive peaks of the sine wave oscillations add with incoming' pulses 'to produce a resultant waveform whose peaks exceed the critical value required to fire said trigger circuit, and forapplying the resultant wave to the grid of the normally non-conductive tube to thereby alter the condition of electrical st a-" bility of` `said trigger circuit,` theconstantshof said trigger being' such'that said trigger circuitA restores `itself to normal after a predetermined time interval, a pair of vacuum tubes each having plate,.grid and cathode electrodes, connections from the `plates .of said vacuum tubes to different outputs of said gaseous tubes, wherebyl said plates obtain at different times from saidl circuitthe polarizing potentials necessary lto er1-T able. the .vacuum .tubes toconduct current, and' a wave distorter, and means including phase, shifter coupling` the grids ofusaid racnum.,tubes"A 15 in common to said generator, through said wave distorter.

14. In a pulse receiving system, a synchronized generator of oscillations of sine Wave form operating at the fundamental pulse frequency, a storage condenser, a rectifier coupled to said storage condenser, means for applying both the incoming pulses and output energy from said generator to said rectifier, said means including a phase shifter for assuring that the positive peaks of said oscillations additively combine with incoming pulses to increase the resultant rectified stored energy onsaid condenser, a discharge path for said condenser comprising a vacuum tube having a control electrode, a circuit for rendering said vacuum tube conductive shortly after the arrival of each incoming pulse, said circuit including a phase shifter coupled to the output of said generator, a wave distorter Whose input is coupled to said phase shifter and whose output is coupled to the control element of said vacuum tube, said Wave distorter altering the sine Wave form of the oscillations impressed thereon to a Wave form having accentuated peaks recurring at the frequency of said generator, an electron discharge device locking circuit under control of 'said vacuum tube, and recording apparatus coupled to an output electrode of said looking circuit.

15. In a pulse receiving system, a generator of oscillations operating at the fundamental pulse frequency, a storage element, a rectifier coupled to said storage element, means for applying the incoming pulses to said rectifier including a transformer, means including said transformer and a phase shifter for applying said oscillations to said rectifier, a space discharge circuit for said storage element, and means including another phase shifter and a wave distorter coupling the output :of said generator to said space discharge circuit for applying periodically recurring peaked waves to said discharge circuit at the frequency of said generator, and an electron tube trigger circuit coupled to said space discharge circuit and responsive to the flow of current therethrough.

16. A pulse receiving system for rebuilding the received pulses into longer duration units comprising a rectangular Wave producing pulse reshaper of the trigger type upon which the received pulses are impressed, a synchronized oscillator, connections for superimposing the output from said oscillator upon the received pulses applied to said reshaper, to thereby produce a resultant wave form whose peaks of a predetermined polarity during actual reception of the incoming pulses exceed the critical value necessary to operate said reshaper, means for producing marking and spacing pulses from the reshaped pulses, said means including a balanced trigger circuit having two degrees of electrical stability, and connections for supplying the input of said balanced trigger circuit from the output of said reshaper under control of the synchronized oscillator.

17. In a pulse receiving system, a synchronized generator, a storage condenser, a rectifier coupled to said storage condenser, means for applying both the incoming pulses and output energy from said generator to said rectifier, said means including a phase shifter for assuring that the peaks of the output Waves from said generator additively combine With incoming pulses to increase the resultant rectified stored energy on said condenser, a discharge path for said condenser comprising a vacuum tube havingr a control electrode, and a circuit for rendering said vacuum tube conductive shortly after the arrival of each incoming pulse, said circuit includingla, wave distorter whose input is coupled to said generator and Whose output is coupled to the control electrode of said vacuum tube, said wave distorter altering the wave form of the generated Waves impressed thereon to a Wave form having accentuated peaks recurring at the frequency of said generator.

18. In a pulse receiving system, a synchronized generator .of oscillations of sine wave form operating at the fundamental pulse frequency, a storage condenser, a rectiiier coupled to said storage condenser, means for applying both the incoming pulses and output energy from said generator to said rectifier, said means including a phase shifter for assuring that the positive peaks of said oscillations additively combine With incoming pulses to increase the resultant rectified stored energy on said condenser, a discharge path for said condenser comprising a vacuum tube having a control electrode, and a circuit for rendering said vacuum tube conductive shortly after the arrival of each incoming pulse, said circuit' including a phase shifter coupled to the output of said generator, a Wave distorter whose input is coupled to said phase shifter'and Whose output is coupled to the control element of said vacuum tube, said Wave distorter altering the sine Wave form of the oscillations impressed thereon to a Wave form having accentuated peaks recurring at .the frequency of said generator, and means for producing marking and spacing pulses from the rectified energy stored on said storage condenser, said last means including a balanced electron discharge device trigger circuit having an input circuit coupled to an electrode of said vacuum tube.

19. In a pulse type communication system wherein pulses are transmitted Whose time duration is shorter than that of the pulse corresponding to one-half a keying cycle, a signal regenerator receiver for rebuilding the received pulses into longer time duration units, said receiver comprising a local oscillator producing sine Wave oscillations synchronized by the incoming pulses and operating at the fundamental pulse frequency, an electronic trigger locking circuit having two degreesV of electrical stability, a Wave reshaper coupling the output of said receiver to said locking circuit, a phase shifter coupling the output of said local oscillator to said locking circuit, whereby said locking circuit is under control of both said wave reshaper and the output of said` oscillator.

20. In a radio telegraph receiving system for receiving pulses representative of intelligence signals transmitted from a remotely located radio transmitter, an electron tube trigger circuit, a generator of sinusoidal oscillations operating at the fundamental pulse frequency, a circuit including a low pass lter for controlling said generator from the output oi said trigger circuit, and means for applying unidirectional pulses representative of the received pulses and the sine Wave output of said generator to said trigger circuit, said means including a phasing circuit for assuring that the positive peaks of sine Wave output from said generator combine with the unidirec-` tional pulses to produce a resultant wave form Whose positive peaks exceed the critical value required to change the 'condition of electrical stability of said trigger circuit.

WARREN BLISS.

`(References on following page) 18 REFERENCES CITED Number Name Date The following references are of record in the 2272070 Reeves Feb 3" 1942 me of this patent: 2,333,281 Wlller Nov. 2, 1943 2,406,019 Labm Aug. 20, 1946 N b UNITED STATES PATENTS 5 OTHER REFERENCES um er lame Date American Standard Denitions of Electrical 1,844,950 Fmcn Feb. 16, 1932 A 4 Terms pubhshed by A. I. E. E., page 203, sectlon 2,053,044 Pierson Sept. 1, 1936 10611734 Ken N0v 24, 1935 65.10.435 and page 229, 65.65.500, copy 1n D1v1- 2,262,838v Deloraine Nov. 1a, 1941 10 Sion 16- 

